Aqueous dispersions of phenyl-betanaphthylamine



Patented Apr. 19, 1949 AQUEOUS DISPERSIONS OF PHENYL-BETA- NAPH'IHYLAMINE Bernard M. Sturgis, Pitman, N. 3., assignor to E. I. du Pont de Nemours & Company, Wilmington, 0151., a, corporation of Delaware No Drawing. Application January 25, 1946, Serial No. 643,486

3 Claims.

This invention relates to the preparation of stable aqueous dispersions of phenyl-beta-naphthylamine, which are particularly useful as antioxidants in the elastomer field. I

The secondary aromatic amines, such as phenyl-beta-naphthylamine, which are employed as anti-oxidants in the rubber and synthetic rubber industries, when employed with rubber latices or other aqueous dispersions of synthetic elastomers are preferably incorporated in such latices as aqueous dispersions. These aqueous dispersions of the amines are prepared with the aid of dispersing agents by the methods usually employed for dispersing solids in liquids. Ordinarily, the aromatic amine anti-oxidant dispersion is made up, as it is used, in concentrations of from to 60%, and such dispersions are added to the latex in carefully measured amounts prior to the coagulation and drying of the elastomer. ondary aromatic amines prepared by the methods heretofore employed are often not stable, and, on standing even for short periods of time, the amine settles out quite rapidly. Such sedimentation makes the handling, measuring and proper addition of the amine to the latex difficult. When such settling out of the dispersion occurs, it tends to plug pumps, valve and lines. It will also be obvious that, in such case, the amount of anti-oxidant actually added to the latex cannot be accurately determined, and therefore it is important, for smooth operation of the process, that stable dispersions of the antioxidants be used.

It is difficult to make stable aqueous dispersions of phenyl-beta-naphthylamine by the usual methods of dispersing solids in water, such as by grinding in a ball mill or even with the use of such efiicient apparatus as the colloid mill. While most of the commercial wetting or dispersing agents give improved results when added to such suspensions, even the most efficient dispersing agents often fail to produce dispersions of phenyl-beta-naphthylamine which will not settle out after short periods of standing. The addition of larger amounts of the dispersing agent does not produce the desired stability.

It is therefore an object of this invention to provide a method of producing aqueous dispersions of phenyl-beta-naphthylamine with improved stability with regard to settling. A further object of the invention is to produce the phenyl-beta-naphthylamine in a form such that it can be readily dispersed in water by the usual The aqueous dispersions of the sec- 2 methods, but which will give suspensions that are much more stable with regard to settling than are ordinarily obtained. A further object of the invention is to produce aqueous dispersions of phenyl-beta-naphthylamine in higher concentrations than has normally been possible and which will remain dispersed when diluted in water for a suflicient time to permit suitable processing of the rubber latices with which they are incorporated.

I have found that greatly improved aqueous dispersions of phenyl-beta-naphthylamine can be produced by adding to the amine a small amount of a liquid polymeric dimethyl silicone. The polymeric silicone is preferably added to the amine during the manufacture or flaking process, as more particularly illustrated in the following examples, although it may be added during the preparation of the dispersion by adding it to the aqueous suspension and subjecting the mass to a milling or colloidal grinding operation. It appearsthat the polymeric silicone must be incorporated in such a manner that it has intimate contact with the dispersed particles of the phenyl-beta-naphthylamine, for, by merely adding the polymericsilicone to the already prepared dispersion without again subjecting the mass to conditions which would ordinarily disperse the solid in a liquid, the same results are not obtained as when the polymeric silicone is added-to the amine during or prior to the dispersion operation. These polymeric silicones are effective as dispersing aids in amounts ranging from 0.1% to 10% although practical limits of use are from 0.1% to 3%. based on the weight of the phenyl-beta-naphthylamine. Mixtures of polymeric silicones of this type appear to be aseffective as'the pure polymeric silicones by themselves. 1

This invention is applicable particularly in improving the dispersion stability of phenyl-betanaphthylamine used as an anti-oxidant for rubber or other elastomers. I,

As pointed out above, the polymeric silicone may be added to the phenyl-beta-naphthylamine during the manufacture of the amine, or it can be intimately incorporated with the amine by a mixing or milling operation so that the amine is put in a form that can be readily dispersed in water by the user by the methods generally employed in preparing the amine dispersion. Alternatively, the polymeric silicone can be added to the water, amine and dispersing agent at the start of the dispersion process, or during the dispersion process. These polymeric silicones will function in any of the common dispersion processes wherein the phenyl-beta-naphthylamine is dispersed in water with a dispersing agent.

The liquid polymeric dimethyl silicones in themselves do not appear to have properties of dispersing agents, and they function as a dispersing aid where the pheny1-beta-naphthyl amine is dispersed in water by means of the usual dispersing agents. The preferred dispersing agent is the sodium salts of the reaction product of naphthalene, formaldehyde, and sulfuric acid, as more particularly disclosed in U. S. Patent 1,336,759. Other dispersing agents, such as the sodium salts of sulfated laurol or other alcohols, or mixtures of the same, purified sulfolignins, and the sodium salts of aliphatic sulfonates of petroleum hydrocarbons or similar dispersing agents, may be employed in place of the sodium salts of the naphthalene-formaldehyde-sulfuric acid condensation product.

The following examples are given to illust ate the invention. The parts used are by weight.

Examp e 1 Gne thousand (.1000) parts of phenyl-betanaphthylamine and 10 parts of a liquid dimethyl silicone polymer with a viscosity of 50 centistokes were melted and naked in a conventional drum type flaker. The flaked material was then made into an equeous dispersion by mixing 300 parts of the flakes, 700 parts of distilled water, and 6 parts of the sodium salts of the acids made by the reaction of naphthalene, formaldehyde, and sulfuric acid. This mixture was ground through :3. Charlotte Colloid Mill set at 0.0055 inch clearance for 20 minutes. In order to test the stability of the dispersion, '75 cc. was placed in a 10 cc. raduated cylinder, brought up to 100 cc. with distilled Wat-er, shaken vigorously and allowed to stand 50: 20 minutes. No sediment could be seen a the bottom of the cyl nd r a nly 2. remain d be d w en the liqui was carefully poured cut, 1 the oth n when o il n as in rporated i he min he resulting aqueous dispersion gave 19 cc. of sediment in the test and this remained in the cylinder after pourice n the q d e silicone used was Dow- Gorning type 200 fluid) Example 2 A liquid dimethyl silicone polymer with a visccsity of 200 c ntistok s used in place of the les viscous material in E amp e ave simila r sults- Emample 3 A liquid dimethyl silicone polymer with a viscosity of 100 centistokes used as in Example 1 gave a somewhat more stable dispersion, only 1 cc. of sediment remaining after pouring off the liquid in the test.

Example 4 methods more particularly disclosed in U. S. Patents 2,258,218 and 2,286,763 to E. C. Rochow. These polymers include those in which a few of the component molecules may originally contain one or three hydrolyzable groups.

The use of the liquid polymeric dimethyl silicones enables the production of greatly improved aqueous dispersions of the phenyl-beta-naphthylamine. These dispersions, being more stable, can

be used over much longer periods of time without settling out. By the addition of the liquid polymeric dimethyl silicones .of the type described as a dispersing aid, greatly improved dispersions are obtained, usually being much smaller in particle size, having lower viscosity for a given concentration, and having less tendency to foam. By the addition of these dispersing aids, much smaller amounts of the dispersing agent may be employed.

The dispersions formed according to the present invention may be added to any aqueous dispersion of oxidizable organic materials requiring stabilization by means of secondary aromatic amines.

Iclaim:

1, In the process for preparing aqueous dispersions of phenyl-beta-naphthylamine wherein the phenyl-beta-naphthylamine is dispersed in water by means of a water soluble dispersing agent, the steps which comprise incorporatin in such aqueous dispersion, before the dispersion process is completed, from 0.1% to 10%, based on the weight of the amine, of a liquid polymeric dimethyl silicone and completing the dispersion process by a colloidal mixing operation.

2. An aqueous dispersion of phenyl-beta-naphthylamine which has been prepared by a colloidal mixing operation and which in addition to the water and phenylebetapnaphthylamine consists of a water soluble dispersin agent and as a dis-.- persing aid from 0.1% to 10%, based on the weight of the amine, of a liquid polymeric dimethyl silicone, which dispersing aid was incors porated in the dispersion prior to completion of the. colloidal mixing operation.

3. A phenylebeta-naphthylamine composition which is readily dispersible in water by a colloidal mixing operation with the aid of a water soluble dispersing agent to give a dispersion which has improved stability with regard to settling, consisting of said amine having intimately incorporated therewith from 0.1% to 1.0%, based on the weight of the amine, of a liquid polymeric dimethyl silicone.

BERNARD M. STURGI S.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Nu Nam Date 1,977,211 Schur 1 Oct. 16, 1934 2,100,714 Hiers Nov. 30, 1937 2,375,007 Larsen 1 May 1, 1945 OTHER REFERENCES Norton in General Electric Review, Aug. 1944, pages .6.-.-16. 

